These districts were set up in the Middle Ages in order to supply troops to the many military companies that were hired to defend Siena as it fought to defend its independence from Florence and other nearby city states. As time has gone by, however, the contrade have lost their administrative and military functions and have instead become simply areas of localised patriotism, held together by the emotions and sense of civic pride of the residents. Their roles have broadened so that every important event - baptisms, deaths, marriages, church holidays, victories at the Palio, even wine or food festivals - is celebrated only within one's own contrada.

Every contrada has its own museum, fountain and baptismal font, motto, allied contrada (only Oca has no allies) and enemy contrada (only four - Bruco, Drago, Giraffa and Selva - have no declared enemies). Real Sienese don't referre to their enemy contrade as an enemy just merely an adversary. Often the adversary contrades share borders.